fix(flatland monokai): change the line highlight color to mach the new background

Original Monokai has a warm/brownish line highlight color which matches perfectly the original warm gray background.
However, the Flatland Monokai version has a cold/bluish gray background which makes the highlight_line look out of place with all the blue from the menus.

![Monokai Screenshot](http://imgur.com/qQjT6an.png)

This commit changes the line highlight color to the same as the standard flatland scheme which has a wonderful combination of background + highlight_line.

Result:
![Monokai new Screenshot](http://imgur.com/yLGpplp.png)

Closes #71
Merge pull request #72 from aristidesfl/monokai

fix(flatland monokai): change the line highlight color to mach the new b...